While continuing to hit Clinton during a rally in Las Vegas, Trump said as he has before that he thinks the Vermont senator should continue to run, despite Clinton securing the delegates necessary for the Democratic nomination.

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"Crazy Bernie" is waiting "for the right thing to happen," Trump said.

"He's waiting for the FBI to do what everyone thinks they're going to do," he continued, referring to the agency's investigation into the private email server Clinton used while serving as secretary of state. "He's saying, 'let's hang in there because it's called the FBI convention.' I think he's waiting for the FBI convention. We'll see if the right things happen."

Sanders has not formally ended his presidential campaign, but Trump said he'll be a "loser" if he does.

"Bernie's in there, and Bernie's fighting, and I don't think he should give up," he said. "If he gives up we'll say, 'Bernie you're a loser, you gave up.'"